Adipose tissue deposition and cellularity in cimaterol-treated female broilers

The effect of feeding a beta agonist, cimaterol, on carcass yield and composition and adipose tissue development was studied in female broilers. Cimaterol was provided at .25 ppm in the feed starting at 4 wk of age. Birds were sacrificed at 4, 6, 8, 10, 12, and 16 wk for determination of eviscerated carcass yield, carcass composition, and growth and cellularity of the abdominal, neck, back, and sartorial adipose depots. Carcass yield was significantly (P less than .01) greater in treated birds than in controls (70.0 vs. 72.8%) at 10 wk of age. Moisture percentage and protein decreased (P less than .05) less rapidly in treated carcasses than in control carcasses with increasing age. Lipid percentage increased (P less than .05) in treated carcasses less rapidly than in control carcasses. The weight of the abdominal fat pad was significantly (P less than .05) lower in treated birds than controls at 16 wk. There were no significant treatment effects on live weights, skeletal growth, or liver weights at any age. The composition of the pectoralis minor was not affected by the treatment. Frequency distributions of adipocyte diameters from the neck and thigh differed from those of the abdominal and back depots at 16 wk. Adipocyte diameter appeared to be more sensitive to the dietary treatment than adipocyte numbers per depot. Both adipocyte size and numbers in each depot continued to increase with increasing age of the broilers. The abdominal fat pad showed the largest percentage increase in cell numbers from 4 to 16 wk of age.